JP7045560B2 - Separation membrane for lithium secondary battery and lithium secondary battery containing it - Google Patents

Description

The present invention relates to a separation film for a lithium secondary battery and a lithium secondary battery including the separation film for a lithium secondary battery, and more specifically, a separation film for a lithium secondary battery capable of improving the performance and safety of the lithium secondary battery and the like. Regarding lithium secondary batteries including.

With the development of technology and increasing demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing, and among such secondary batteries, they show high energy density and operating potential, and have a long cycle life. Therefore, lithium secondary batteries with a low self-discharge rate have been commercialized and widely used.

Recently, as interest in environmental issues has increased, electric vehicles (EVs) and hybrid electric vehicles (EVs) and hybrid electric vehicles (EVs) that can replace fossil fuel-based vehicles such as gasoline-powered vehicles and diesel-powered vehicles, which are one of the major causes of air pollution. A lot of research on HEV) etc. is underway.

For such electric vehicles (EVs), hybrid electric vehicles (HEVs), etc., as a power source, a nickel hydrogen metal (Ni-MH) secondary battery or lithium having high energy density, high discharge voltage, and output stability. Secondary batteries are used, but when lithium secondary batteries are used in electric vehicles, they must be used for 10 years or more under harsh conditions, as well as having high energy density and characteristics that can exhibit large output in a short time. Therefore, it is inevitably required to have much better energy density, safety and long life characteristics than existing small lithium secondary batteries.

Generally, a lithium secondary battery is manufactured by using an anode and a cathode, a separator interposed between them, and an electrolyte which is a transmission medium for lithium ions.

Among them, the separation film is an inactive material that does not participate in the electrochemical reaction, but is a material that provides a path for lithium ions to move in order to operate the battery and separates the physical contact between the positive electrode and the negative electrode. It is one of the core materials that have a great influence on the performance and stability of batteries.

The manufacturing method of the separation film is roughly divided into wet and dry methods. In the wet manufacturing method, a polymer material and a low molecular weight wax are mixed, the film is extruded at a high temperature, and then the wax is extracted using a solvent (solvent). It is a method of forming a fine porous structure, and the dry manufacturing method is a multi-layer structure in which polyethylene (PE) and polypropylene (PP) are used to join with a two- or three-layer film, and is physically physical without using wax. It is a method of manufacturing by creating pores only by stretching and heat treatment.

On the other hand, the lithium secondary battery tends to generate heat due to the kinetic energy generated during repeated charging and discharging, but the separation membrane is vulnerable to this heat. In particular, in the case of a separation film using polyethylene (PE), a "shutdown" phenomenon may occur in which a separation film using polyethylene (PE) begins to melt (melt) at about 130 ° C and the pores are closed. Can not be prevented and may collapse (meltdown or mechanical integrity destruction).

In order to overcome such problems, recently, research is continuing to enhance durability, such as using a dip coating method in which the surface of the separation membrane is coated with both inorganic particles and a polymer binder. ..

On the other hand, in conventional secondary batteries, a liquid electrolyte, particularly an ionic conductive organic liquid electrolyte in which a salt is dissolved in a non-aqueous organic solvent, has been mainly used.

However, when a liquid electrolyte is used in this way, not only is there a high possibility that the electrode material will deteriorate and the organic solvent will volatilize, but there will also be safety problems such as combustion due to the ambient temperature and the temperature rise of the battery itself. Occurs. In particular, the lithium secondary battery has a problem that gas is generated inside the battery due to decomposition of the carbonate organic solvent and / or a side reaction between the organic solvent and the electrode during charging / discharging, and the thickness of the battery is expanded. be. Therefore, the deterioration of battery performance and safety is indispensable.

Generally, the safety of a battery is improved in the order of liquid electrolyte <gel polymer electrolyte <solid polymer electrolyte, but it is known that the battery performance is decreased in the order of liquid electrolyte <gel polymer electrolyte <solid polymer electrolyte. It is known that it has not been commercialized because it is inferior.

On the other hand, the gel polymer electrolyte has excellent electrochemical safety, but the adhesive strength between the electrode and the electrolyte is improved due to the unique gel-like adhesive strength, and a thin-film battery can be manufactured. Therefore, various lithium secondary batteries have recently been produced. Applied to batteries. However, when the gel polymer electrolyte and the separation membrane on which the coating layer containing the inorganic particles are formed are used together, there is a problem that the stability and performance of the secondary battery are deteriorated because the adhesive force between the coating layer and the electrolyte is low. There is.

Therefore, separation for a lithium secondary battery, which has excellent durability and adhesion to a gel polymer electrolyte, improves the safety of a lithium secondary battery, and can have a life characteristic and a capacity characteristic of a certain level or more. It is the actual situation that the development of the membrane is necessary.

Korean Published Patent No. 10-2015-0131513

The present invention is for solving the above-mentioned problems, and can be applied to various battery forms while increasing the adhesion with the gel polymer electrolyte and improving the performance and safety of the battery. , A separation film for a lithium secondary battery in which a coating layer having a multilayer structure that is easy to manufacture is formed, and a lithium secondary battery including the separation film.

In one aspect, the invention is a lithium secondary comprising a substrate, a first coating layer containing a first organic binder containing an ethylenically unsaturated group, and a second coating layer containing a second organic binder and inorganic particles. A separating film for a battery is provided.

At this time, the first coating layer may be formed on the surface of the base material, and the second coating layer may be formed on the first coating layer.

On the other hand, the second coating layer may be formed on the surface of the base material, and the first coating layer may be formed on the second coating layer.

In another aspect, the present invention forms a first coating layer containing a first organic binder containing an ethylenically unsaturated group and a second coating layer containing a second organic binder and inorganic particles on the surface of the substrate. Provided is a method for manufacturing a separation film for a lithium secondary battery, which comprises a step.

In another aspect, the present invention includes at least one positive electrode, at least one negative electrode, and at least one or more first separation films interposed between the positive electrode and the negative electrode. Contains an electrode assembly containing a unit cell of the above and a second separation film interposed between the unit cells, and a gel polymer electrolyte formed by polymerizing an oligomer containing a (meth) acrylate group. The separation film and the second separation film include a first coating layer containing a first organic binder containing an ethylenically unsaturated group and a second coating layer containing a second organic binder and inorganic particles, and the ethylenically unsaturated film is contained. Provided is a lithium secondary battery in which a first organic binder containing a group and an oligomer containing the (meth) acrylate group are polymerized to form a polymer network having a three-dimensional structure.

The separation film according to the present invention contains a first organic binder containing an ethylenically unsaturated group in the first coating layer, and the ethylenically unsaturated group reacts with the oligomer contained in the gel polymer electrolyte composition to form a separation film. The adhesion to the gel polymer electrolyte is improved, thereby improving the performance and stability of the lithium secondary battery.

Further, the separation film according to the present invention is a lithium secondary battery manufactured through a high temperature step such as a lamination step when a second coating layer containing a second organic binder and inorganic particles is formed on the first coating layer. It is possible to prevent the ethylenically unsaturated group from being exposed to a high temperature even when manufacturing the battery, and when it is formed under the first coating layer, the battery can be manufactured under various conditions. The processability can be improved.

Therefore, not only the durability of the separation film can be improved, but also it can be used as a separation film for a lithium secondary battery having various structures, so that the manufacturing process of the lithium secondary battery can be improved.

Hereinafter, the present invention will be described in more detail.

The terms and words used herein and in the scope of the claims shall not be construed in a general or lexical sense only and the inventor shall explain his invention in the best possible way. , In line with the principle that the concept of terms can be defined as appropriate, it must be interpreted as a meaning and concept that fits the technical idea of the present invention.

The terms used herein are merely used to illustrate exemplary embodiments and the like, and are not intended to limit the invention. A singular expression includes multiple expressions unless they are meant to be explicitly different in context.

As used herein, terms such as "include", "prepare" or "have" are intended to specify the existence of implemented features, numbers, stages, components or combinations thereof. , One or more other features, numbers, stages, components, or combinations thereof must be understood as not preliminarily excluding the existence or addability.

In the present specification, the weight average molecular weight may mean a conversion value with respect to standard polystyrene measured by GPC (Gel Permeation Chromatography), and unless otherwise specified, the molecular weight may mean a weight average molecular weight. At this time, the weight average molecular weight can be measured by using gel permeation chromatography (GPC). For example, after preparing a sample of a constant concentration, the GPC measurement system alliance 4 instrument is stabilized. Once the instrument is stabilized, the standard sample and sample sample are injected into the instrument to obtain a chromatogram, and then the weight average molecular weight is calculated by an analytical method (system: Alliance 4, column: Ultrahydrogel linear x 2, element: 0). .1M NaNO ₃ (pH 7.0 phosphate buffer, flow rate: 0.1 mL / min, temper: 40 ° C., injection: 100 μL)

<Separation membrane for lithium secondary battery>
The separation membrane for a lithium secondary battery according to the present invention includes a first coating layer containing a first organic binder containing an ethylenically unsaturated group, and a second coating layer containing a second organic binder and inorganic particles.

Conventionally, the surface of the base material is coated with inorganic particles or the like in order to improve the durability and conductivity of the separation membrane, but the inorganic particles and the existing binder and the like have a binding force with the gel polymer electrolyte. There is a problem that the adhesion to the electrolyte is remarkably lowered because the particle size is low and the polymerization reaction and the like cannot proceed. If the adhesion between the electrolyte and the separation membrane is reduced, the safety of the battery may be reduced, for example, an internal short circuit of the battery may be induced.

Therefore, the inventor of the present invention has devised a separation film that further forms a separate layer containing a first organic binder containing an ethylenically unsaturated group in addition to the existing inorganic particle coating layer. The ethylenically unsaturated group contained in the first organic binder can undergo a radical polymerization reaction with the oligomer contained in the composition for a gel polymer electrolyte.

More specifically, the composition for a gel polymer electrolyte may contain an oligomer containing a (meth) acrylate group, an amide group, an oxyalkylene group, a siloxane group and the like, and the functional group contained in the oligomer is the functional group. It is a functional group capable of radical polymerization reaction with the ethylenically unsaturated group contained in the first organic binder. Therefore, the oligomer and the first organic binder may be bonded to a three-dimensional structure through a radical polymerization reaction in the curing process of the composition for gel polymer electrolyte, and as a result, the adhesion between the separation membrane and the gel polymer electrolyte is improved. Can be made to. On the other hand, in the case of the present invention, the adhesion between the separation membrane and the gel polymer electrolyte is improved by the first coating layer containing the first organic binder, and of course, the second coating layer containing the second organic binder improves the adhesion between the separation membrane and the gel polymer electrolyte. The adhesive strength between the separation membrane and the electrode can also be maintained constant. Further, in the case of the separation film for a lithium secondary battery according to the present invention, the stacking order of the first and second coating layers may be different in consideration of the structure of the battery to be manufactured, the intended use, the battery manufacturing process, and the like.

At this time, the thickness of the separation membrane may be 0.1 to 20 μm, preferably 0.5 to 20 μm, and more preferably 1.0 to 20 μm. When the thickness of the separation membrane is formed to the thickness, the mechanical properties and high temperature durability of the separation membrane can be maintained constant.

As the substrate, a porous substrate may be used, and the ordinary porous substrate can be used without any special limitation as long as it can be used as a separation membrane material for an electrochemical element. Examples of such a porous substrate include polyolefin, polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene. Among the above-mentioned polymer resins, there are a non-woven fabric formed of at least one of them, a porous polymer film, or a laminate of two or more of these, but the present invention is not particularly limited thereto.

The first coating layer is for improving the adhesion between the gel polymer electrolyte and the separation membrane, and contains a first organic binder containing an ethylenically unsaturated group. The ethylenically unsaturated group is bonded to the oligomer contained in the composition for gel polymer electrolyte via a radical polymerization reaction.

For example, the ethylenically unsaturated group may contain at least one selected from the group consisting of a vinyl group, an acrylic oxy group and a methacrylic oxy group.

On the other hand, in the first organic binder, in addition to the functional group, an alkylene group, an alkylene oxide group, and a halogen element (F, Cl, Br) in which at least one halogen element (F, Cl, Br, I) is substituted are used. , I) may further comprise a unit comprising at least one selected from the group consisting of substituted alkylene oxide groups, imide groups and celluloids.

At this time, in the case of the ethylenically unsaturated group, it may be located at the terminal portion of the polymer main chain or the side surface portion of the polymer main chain, which is the unit, and the number or position of the functional group to be attached is not specified.

For example, the unit containing at least one substituted alkylene group for the halogen element may be represented by at least one selected from the units represented by the following chemical formulas X-1 to X-6.

前記化学式Ｘ－１において、前記ｍ１は、１から１００の整数である。

In the chemical formula X-1, the m1 is an integer from 1 to 100.

前記化学式Ｘ－２において、前記ｍ２及びｍ３は、それぞれ独立して１から１００の整数である。

In the chemical formula X-2, m2 and m3 are independently integers from 1 to 100, respectively.

前記化学式Ｘ－３において、前記ｍ４は、１から１００の整数である。 For example, the unit containing an alkylene oxide group may be represented by the following chemical formula X-3.

In the chemical formula X-3, m4 is an integer from 1 to 100.

前記化学式Ｘ－４において、前記ｍ５は、１から１００の整数である。 For example, the unit containing the alkylene oxide group substituted with the halogen element may be represented by the following chemical formula X-4.

In the chemical formula X-4, m5 is an integer from 1 to 100.

前記化学式Ｘ－５において、前記ｍ６は、１から１００の整数である。 For example, the unit containing the imide group may be represented by the following chemical formula X-5.

In the chemical formula X-5, m6 is an integer from 1 to 100.

前記化学式Ｘ－６において、前記ｍ７は、１から１００の整数である。 For example, the unit containing the celluloid may be represented by the following chemical formula X-6.

In the chemical formula X-6, m7 is an integer from 1 to 100.

Specifically, the compound used as the first organic binder is formed on the terminal portion or the side surface portion of the polymer main chain containing at least one unit selected from the group consisting of the chemical formulas X-1 to X-6. It is a compound located in which an ethylenically unsaturated group is substituted.

For example, in the case of a polymer or copolymer containing a unit represented by the chemical formulas X-1 to X-6, it is generally formed by a free radical reaction or the like. At this time, end-capping is performed at the final stage of the polymerization reaction, and a halogen element is contained in the terminal portion and the side surface portion of the main chain forming the polymer or the copolymer so that the polymerization reaction does not occur any more. A functional group, a hydroxy group, an alkyl oxide group, an alkyl group, etc. are attached.

For example, when the terminal is treated with a functional group containing a halogen element, a halogen compound such as sodium chloride (NaCl) may be used as the end-capping agent, but the method is limited to the above method. However, the type of terminal capping agent is also not limited to the above-mentioned substances.

For example, when a halogen element or the like is located at the terminal portion or the side surface portion, when it is reacted with a (meth) acrylate compound or a vinyl compound or the like, the halogen element at the terminal portion becomes a (meth) acrylic oxy group or a vinyl group or the like. Is substituted with an ethylenically unsaturated group. A first organic binder having an ethylenically unsaturated group can be produced through the reaction.

The first organic binder may be used alone for the first coating layer, or 1 part by weight to 80 parts by weight, preferably 5 parts by weight to 60 parts by weight, based on 100 parts by weight of the first coating layer. It may be preferably contained in an amount of 5 to 40 parts by weight. When the first organic binder is contained in the above range, the binding force with the gel polymer electrolyte can be maintained above a certain level.

On the other hand, the first coating layer may further contain inorganic particles in addition to the first organic binder, and the content thereof may be contained in the rest of the first coating layer excluding the first organic binder. Inorganic particles will be described more specifically below.

The second coating layer enhances the durability of the separation film base material and is immediately formed on the surface of the base material in order to improve the processability depending on the stacking order, or when it undergoes a lamination step or the like, it is on the first coating layer. The first coating layer is formed in the above and is for preventing the first coating layer from being exposed to a high temperature, and contains a second organic binder and inorganic particles.

The second organic binder is used for immobilizing inorganic particles.

As the second organic binder, a normal binder may be used. More specifically, the second organic binder contains an alkylene group, an alkylene oxide group, and a halogen element (F, Cl, Br, I) in which at least one halogen element (F, Cl, Br, I) is substituted. May include polymers containing at least one unit selected from the group consisting of substituted alkylene oxide groups, imide groups, and celluloids.

For example, the second organic binder may contain a polymer containing at least one unit selected from the group consisting of the chemical formulas X-1 to X-6, with respect to the chemical formulas X-1 to X-6. Since it is the same as the above-mentioned one, the description thereof will be omitted.

For example, the second organic binder may include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, etc., but is limited to the above-mentioned types. is not it.

On the other hand, as the second organic binder, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, which are usually used in addition to the polymer containing the unit represented by the chemical formula. , Hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, etc. Various copolymers and the like may be used.

The second organic binder is contained in an amount of 1 part to 80 parts by weight, preferably 5 parts by weight to 60 parts by weight, and more preferably 5 parts by weight to 40 parts by weight with respect to 100 parts by weight of the second coating layer. You can do it. When the second organic binder is contained within the above range, the detachment of the inorganic particles can be prevented, and the adhesive strength and the mechanical performance can be maintained at a certain level or higher.

The inorganic particles play a role of forming an interstitial volume between particles to form pores of micro units, and also serve as a kind of spacer capable of maintaining a physical form. Further, since the inorganic particles can transmit and move lithium ions, the lithium ion conductivity can be improved. At this time, by adjusting the size of the inorganic particles, the content of the inorganic particles, and the composition of the inorganic particles and the polymer, pores in micro units can be formed, and the size and degree of pores can be adjusted.

The inorganic particles may contain inorganic particles commonly used in the art. For example, the inorganic particles contain at least one element selected from the group consisting of Si, Al, Ti, Zr, Sn, Ce, Mg, Ca, Zn, Y, Pb, Ba, Hf, and Sr. It may contain at least one element selected from the group consisting of Si, Al, Ti and Zr.

More specifically, the inorganic particles include SiO ₂ , Al ₂ O ₃ , TIO ₂ , ZrO ₂ , SnO ₂ , CeO ₂ , MgO, CaO, ZnO, Y ₂ O ₃ , Pb (Zr, Ti) O ₃ . (PZT), Pb _(1-a1) La _a1 Zr _(1-b1) Ti _b1 O ₃ (0 ≦ a1 ≦ 1, 0 ≦ b1 ≦ 1, PLZT), PB (Mg ₃ Nb _2/3 ) O ₃ － There are PbTiO ₃ (PMN-PT), BaTiO ₃ , HfO ₂ (hafnia), SrTiO ₃ , etc., and the above-arranged inorganic substances generally have the property that their physical properties do not change even at a high temperature of 200 ° C. or higher. Have. More preferably, the inorganic particles may contain at least one or more inorganic substances selected from the group consisting of SiO ₂ , Al ₂ O ₃ , TiO ₂ and ZrO ₂ .

The inorganic particles may be contained in 100 parts by weight of the second coating layer in the balance excluding the second organic binder.

<Manufacturing method of separation membrane for lithium secondary battery>
Next, a method for manufacturing a separation membrane for a lithium secondary battery according to the present invention will be described. The separation film for a lithium secondary battery according to the present invention includes a first coating layer containing a first organic binder containing an ethylenically unsaturated group on the surface of a base material, and a second coating layer containing a second organic binder and inorganic particles. It is manufactured through the steps of forming.

For example, after forming the first coating layer on the substrate, a second coating layer may be formed on the first coating layer. As another example, after forming the second coating layer on the substrate, the first coating layer may be formed on the second coating layer.

On the other hand, depending on the order of formation of the first and second coating layers, a lithium secondary battery laminated in the order of base material / first coating layer / second coating layer or base material / second coating layer / first coating layer. A separation film may be formed. Since the reasons for different stacking orders have already been described, the description thereof will be omitted.

The first coating layer may be formed under temperature conditions of 40 ° C. to 110 ° C., preferably 50 ° C. to 110 ° C., more preferably 60 ° C. to 110 ° C. If the first coating layer is formed under the temperature conditions, the coating can be easily performed while minimizing the damage of the ethylenically unsaturated group.

More specifically, a first coating layer composition containing a first organic binder containing an ethylenically unsaturated group is produced. At this time, an organic solvent or the like may be used as the solvent in addition to the first organic binder. For example, N-methylpyrrole, acetone and the like may be used, but the solvent is not limited to the type. The solvent contains 10 parts by weight to 50 parts by weight, preferably 10 parts by weight to 40 parts by weight, based on 100 parts by weight of the whole first coating layer composition. May be included. When the solvent is contained in the above range, the coating is easy and the processability can be improved.

The second coating layer may be formed under temperature conditions of 120 ° C to 200 ° C, preferably 120 ° C to 190 ° C, more preferably 120 ° C to 180 ° C. If the second coating layer is formed under the temperature conditions, the solvent used in the step of forming the coating layer can be effectively removed while preventing damage to the separation film.

More specifically, a second coating layer composition containing a second organic binder and inorganic particles is produced. At this time, in addition to the second organic binder and the inorganic particles, a solvent usually used for separation membrane coating may be used as a solvent. For example, N-methylpyrrole or the like may be used. The solvent contains 10 parts by weight to 50 parts by weight, preferably 10 parts by weight to 40 parts by weight, based on 100 parts by weight of the whole of the second coating layer composition. It may be included so as to be. When the solvent is contained in the above range, the coating is easy and the processability can be maintained at a certain level or higher.

<Lithium secondary battery>
Next, the lithium secondary battery according to the present invention will be described. Lithium secondary batteries according to yet another embodiment of the present invention include an electrode assembly and a gel polymer electrolyte.

More specifically, the electrode assembly comprises at least one positive electrode, at least one negative electrode, and at least one first separation membrane interposed between the positive electrode and the negative electrode. It includes one or more unit cells and a second separation membrane interposed between the unit cells. At this time, since the first separation membrane and the second separation membrane use the separation membrane, the content thereof is the same as the above-mentioned content, but a specific description thereof will be omitted.

The positive electrode may be produced by coating a positive electrode current collector with a positive electrode active material slurry containing a positive electrode active material, a binder for electrodes, a conductive material, a solvent, and the like.

The positive current collector is not particularly limited as long as it has conductivity without inducing a chemical change in the battery, and is, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or. A surface-treated aluminum or stainless steel surface with carbon, nickel, titanium, silver or the like may be used.

The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, specifically, one or more metals such as cobalt, manganese, nickel or aluminum and lithium. It may contain a lithium composite metal oxide containing. More specifically, the lithium composite metal oxide is a lithium-manganese oxide (for example, LiMnO ₂ , LiMn ₂ O ₄ or the like), a lithium-cobalt oxide (for example, LiCoO ₂ or the like), or a lithium-nickel. System oxides (eg LiNiO ₂ etc.), Lithium-nickel-manganese oxides (eg LiNi _1-Y1 Mn _Y1 O ₂ (here 0 <Y1 <1), LiMn _2-z1 Ni _z1 O ₄ (eg, LiMn 2-z1 Ni z1 O 4) Here, 0 <Z1 <2), etc.), lithium-nickel-cobalt oxide (for example, LiNi _1-Y2 Co _Y2 O ₂ (here, 0 <Y2 <1), etc.), lithium-manganese-cobalt system. Oxides (eg, LiCo _1-Y3 Mn _Y3 O ₂ (here 0 <Y3 <1), LiMn _{2-z2 Coz2} O ₄ (here 0 <Z2 <2), etc.), lithium-nickel-manganese -Cobalt oxide (eg, Li (Ni _p1 Co _q1 Mn _r1 ) O ₂ (where 0 <p1 <1, 0 <q1 <1, 0 <r1 <1, p1 + q1 + r1 = 1) or Li (Ni _p2 ) Co _q2 Mn _r2 ) O ₄ (where 0 <p2 <2, 0 <q2 <2, 0 <r2 <2, p2 + q2 + r2 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (For example, Li (Ni _p3 Co _q3 Mn _r3 M _S1 ) O ₂ (Here, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p3, q3, r3. And, s1 is an atomic fraction of each independent element, and 0 <p3 <1, 0 <q3 <1, 0 <r3 <1, 0 <s1 <1, p3 + q3 + r3 + s1 = 1), etc.) Etc., and any one or more of these compounds may be contained.

Among these, the lithium composite metal oxide is LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , or lithium nickel manganese cobalt oxide (for example, Li (Ni _0.6 )) in that the capacity characteristics and stability of the battery can be improved. Mn _0.2 Co _0.2 ) O ₂ , Li (Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ , or Li (Ni _0.8 Mn _0.1 Co _0.1 ) O ₂ etc.) , Or lithium nickel-cobalt aluminum oxide (for example, LiNi _0.8 Co _0.15 Al _0.05 O ₂ etc.), and control of the type and content ratio of the constituent elements forming the lithium composite metal oxide. When considering the remarkable improvement effect due to, the lithium composite metal oxide is Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ , Li (Ni _0.5 Mn _0.3 Co _0.2 ). ) O ₂ , Li (Ni _0.7 Mn _0.15 Co _0.15 ) O ₂ or Li (Ni _0.8 Mn _0.1 Co _0.1 ) O ₂ or the like, and any of these. One or more mixtures may be used.

The positive electrode active material is 60% by weight to 98% by weight, preferably 70% by weight to 98% by weight, more preferably 80% by weight to 98% by weight, based on the total weight of the solid matter excluding the solvent in the positive electrode active material slurry. May be included in% by weight.

The binder for electrodes is a component that assists in binding an active material to a conductive material or the like and to a current collector. Specifically, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-dienter polymer (EPDM). , Sulfated EPDM, styrene-butadiene rubber, fluororubber, various copolymers and the like. Usually, the binder for an electrode is from 1% by weight to 20% by weight, preferably from 1% by weight to 15% by weight, more preferably from 1% by weight, based on the total weight of the solid matter excluding the solvent in the positive electrode active material slurry. It may be contained in 10% by weight.

The conductive material is a component for further improving the conductivity of the positive electrode active material. The conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery. For example, graphite; carbon black, acetylene black, ketjen black, channel black, etc. Carbon-based substances such as furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powder such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used. Specific examples of commercially available conductive materials include Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company products, etc., which are acetylene black series. There are Chevron Black, EC series (Armak Company products), Vulcan XC-72 (Cabot Company products) and Super P (Timecal products). The conductive material may be contained in the positive electrode active material slurry in an amount of 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight based on the total weight of the solid matter excluding the solvent. ..

The solvent may contain an organic solvent such as NMP (N-methyl-2-pyrrolidone), and when the positive electrode active material and optionally a binder, a conductive material and the like are contained. It may be used in an amount that gives a preferable viscosity. For example, the concentration of the positive electrode active material and optionally the solid content containing the binder and the conductive material is 60% by weight to 95% by weight, preferably 70% by weight to 95% by weight, more preferably 70% by weight to 90% by weight. May be included to be.

The negative electrode may be manufactured, for example, by coating a negative electrode current collector with a negative electrode active material slurry containing a negative electrode active material, a binder for electrodes, a conductive material, a solvent, and the like.

The negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it has high conductivity without inducing a chemical change in the battery, and is not particularly limited, for example, copper, stainless steel, aluminum, nickel, titanium. , A surface-treated surface of calcined carbon, copper or stainless steel with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy or the like may be used. Further, fine irregularities may be formed on the surface to strengthen the bonding force of the negative electrode active material, and the film, sheet, foil, net, porous body, foam, non-woven fabric and the like may be used in various forms.

Examples of the negative electrode active material include natural graphite, artificial graphite, and carbonaceous materials; metals such as lithium-containing titanium composite oxide (LTO), Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe (Me). ); Alloys composed of the metals (Me); Oxides (MeOx) of the metals (Me); and one selected from the group consisting of a composite of the metals (Me) and carbon. Alternatively, two or more kinds of negative electrode active materials can be mentioned.

The negative electrode active material is 60% by weight to 98% by weight, preferably 70% by weight to 98% by weight, more preferably 80% by weight to 98% by weight, based on the total weight of the solid matter excluding the solvent in the negative electrode active material slurry. May be included in% by weight.

Since the contents of the binder for electrodes, the conductive material and the solvent are the same as those described above, specific description thereof will be omitted.

The gel polymer electrolyte is formed by polymerizing an oligomer containing a (meth) acrylate group. When the oligomer containing the (meth) acrylate group is used, a polymer network having a three-dimensional structure can be formed by forming a radical polymerization reaction with the first organic binder contained in the first coating layer.

For example, the oligomer may further contain an oxyalkylene group. Specifically, the oligomer may be represented by the following chemical formula 1.

In the chemical formula 1, A and A'are units each independently containing a (meth) acrylate group, and C ₁ is a unit containing an oxyalkylene group.

Specifically, the units A and A'are units containing a (meth) acrylate group so that the oligomer can be polymerized. When it contains a (meth) acrylate group, it can react with the ethylenically unsaturated group contained in the first organic binder to form a polymer network. The units A and A'may be derived from a monomer containing monofunctional or polyfunctional (meth) acrylate or (meth) acrylic acid.

For example, the units A and A'may independently contain at least one of the units represented by the following chemical formulas A-1 to A-5.

前記化学式Ｃ_１－１において、Ｒは、炭素数１から１０の置換又は非置換された直鎖状又は分枝鎖状アルキレン基であり、ｋ１は、１から３０の整数である。 The unit C1 may include a unit represented by the chemical formula C1-1.

In the chemical formula C 1-1, R is a substituted or substituted linear or branched alkylene group having ₁ to 10 carbon atoms, and k1 is an integer of 1 to 30.

As another example, in the chemical formula C _1-1 , the R may be independently -CH ₂ CH _2- or -CHCH ₃ CH _2- .

前記化学式１－１において、前記ｎ１は、１から２０，０００の整数である。 For example, according to one embodiment of the present invention, the oligomer may be at least one compound selected from the group consisting of the following chemical formulas 1-1 to 1-5.

In the chemical formula 1-1, n1 is an integer of 1 to 20,000.

前記化学式１－２において、前記ｎ２は、１から２０，０００の整数である。

In the chemical formula 1-2, the n2 is an integer of 1 to 20,000.

前記化学式１－３において、前記ｎ３は、１から２０，０００の整数である。

In the chemical formula 1-3, the n3 is an integer of 1 to 20,000.

前記化学式１－４において、前記ｎ４は、１から２０，０００の整数である。

In the chemical formula 1-4, the n4 is an integer of 1 to 20,000.

前記化学式１－５において、前記ｎ５は、１から２０，０００の整数である。

In the chemical formula 1-5, the n5 is an integer of 1 to 20,000.

In the chemical formulas 1-1 to 1-5, n1 to n5 are independently integers of 1 to 20,000, preferably integers of 1 to 10,000, and more preferably 1 to 1, respectively. It is an integer of 5,000.

As another example, the oligomer may be represented by the following chemical formula 2.

In the chemical formula 2, A and A'are units each independently containing a (meth) acrylate group and are the same as those described above, and B and B'are independently amides. A unit containing a group, C ₂ and C _2'are units containing an oxyalkylene group independently, D is a unit containing a siloxane group, and l is an integer from 1 to 200. be.

On the other hand, l may be preferably an integer of 10 to 200, more preferably an integer of 1 to 150. When l is within the above range, the mechanical properties of the polymer formed by the oligomer are high, the fluidity is maintained above a certain level and uniformly dispersed inside the battery, and the wettability is maintained above a certain level. obtain.

Further, the units B and B'are units each independently containing an amide group, and are for adjusting the ion transfer characteristics and imparting mechanical properties in the realization of the polymer electrolyte. For example, the units B and B'may independently contain units represented by the following chemical formula B-1.

In the chemical formula B-1, R ″ is derived from a linear or non-linear alkylene group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkylene group having 3 to 10 carbon atoms, and 6 carbon atoms. 20 substituted or unsubstituted bicycloalkylene group, substituted or unsubstituted arylene group having 6 to 20 carbon atoms, a unit represented by the following chemical formula R''-1 and the following chemical formula R''-2. At least one selected from the group consisting of units.

As another example, in the chemical formula B-1, the R ″ may contain at least one of the units represented by the following chemical formulas R ″ -3 to R ″ -8.

Further, in the realization of the polymer electrolyte of the present invention, the units C ₂ and C _2'are independent units containing an oxyalkylene group. The units C ₂ and C _2'are used to regulate salt dissociation and ion transfer capacity within the polymer network.

For example, the units C ₂ and C _2'may independently contain units represented by the chemical formula C _2-1 .

前記化学式Ｃ_２－１において、Ｒ’は、炭素数１から１０の置換又は非置換された直鎖状又は分枝鎖状のアルキレン基であり、ｋ２は、１から３０の整数である。

In the chemical formula C2-1, _R'is a substituted or substituted linear or branched alkylene group having 1 to 10 carbon atoms, and k2 is an integer of 1 to 30.

As another example, in the chemical formula C2-1, the R'may be -CH ₂ CH _2- or -CHCH ₃ CH _2- .

Further, the unit D is for adjusting the mechanical properties containing a siloxane group and the affinity with the separation membrane. Specifically, it is possible to form a structure in the polymer network for ensuring flexibility other than the hard structural region due to the amide bond.

For example, the unit D may include a unit represented by the chemical formula D-1.

In the chemical formula D-1, R ₁ and R ₂ are linear or non-linear alkylene groups having 1 to 5 carbon atoms, and R ₃ , R ₄ , R ₅ and R ₆ are independent of each other. It is a hydrocarbon, an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 12 carbon atoms, and g1 is an integer of 1 to 400. On the other hand, the g1 may be preferably an integer of 1 to 300, more preferably an integer of 1 to 200.

As another example, the unit D may include a unit represented by the following chemical formula D-2.

In the chemical formula D-2, R ₃ , R ₄ , R ₅ and R ₆ are independently hydrogen, an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 12 carbon atoms, respectively, and g2 is 1 It may be an integer from to 400, preferably an integer from 1 to 300, and more preferably an integer from 1 to 200.

More specifically, the D-1 may be at least one selected from the units represented by the following chemical formulas D-3 and D-4.

In the chemical formulas D-3 and D-4, g3 and g4 may be independently an integer of 1 to 400, preferably an integer of 1 to 300, and more preferably an integer of 1 to 200, respectively.

For example, according to one embodiment of the present invention, the oligomer may be at least one compound selected from the group consisting of the compounds represented by the following chemical formulas 2-1 to 2-5.

前記化学式２－１において、前記ｋ３及びｋ４は、それぞれ独立して１から３０の整数であり、前記ｇ５は、１から４００の整数である。前記ｌ１は、１から２００の整数である。

In the chemical formula 2-1 the k3 and k4 are independently integers of 1 to 30, and the g5 is an integer of 1 to 400, respectively. The l1 is an integer from 1 to 200.

前記化学式２－２において、前記ｋ５及びｋ６は、それぞれ独立して１から３０の整数であり、前記ｇ６は、１から４００の整数である。前記ｌ２は、１から２００の整数である。

In the chemical formula 2-2, the k5 and k6 are independently integers of 1 to 30, and the g6 is an integer of 1 to 400, respectively. The l2 is an integer from 1 to 200.

前記化学式２－３において、前記ｋ７及びｋ８は、それぞれ独立して１から３０の整数であり、前記ｇ７は、１から４００の整数である。前記ｌ３は、１から２００の整数である。

In the chemical formula 2-3, the k7 and k8 are independently integers of 1 to 30, and the g7 is an integer of 1 to 400, respectively. The l3 is an integer from 1 to 200.

前記化学式２－４において、前記ｋ９及びｋ１０は、それぞれ独立して１から３０の整数であり、前記ｇ８は、１から４００の整数である。前記ｌ４は、１から２００の整数である。

In the chemical formula 2-4, the k9 and k10 are independently integers of 1 to 30, and the g8 is an integer of 1 to 400, respectively. The l4 is an integer from 1 to 200.

前記化学式２－５において、前記ｋ１１及びｋ１２は、それぞれ独立して１から３０の整数であり、前記ｇ９は、１から４００の整数である。前記ｌ５は、１から２００の整数である。

In the chemical formula 2-5, k11 and k12 are independently integers of 1 to 30, and g9 is an integer of 1 to 400, respectively. The l5 is an integer from 1 to 200.

On the other hand, in the chemical formulas 2-1 to 2-5, l1 to l5 may be independently, preferably an integer of 1 to 150, and more preferably an integer of 1 to 100, respectively. When l1 to l5 are within the above range, the mechanical properties of the polymer formed by the oligomer are high, the fluidity is maintained at a certain level or higher, and the polymer can be uniformly dispersed inside the battery.

Further, the oligomer of the present invention may have a weight average molecular weight of about 1,000 to 100,000. When the weight average molecular weight of the oligomer is within the above range, the mechanical strength of the battery containing the oligomer can be effectively improved.

On the other hand, the gel polymer electrolyte is preferably formed by injecting a composition for a gel polymer electrolyte containing the oligomer into a battery case and then curing the composition.

More specifically, in the secondary battery according to the present invention, (a) the stage of inserting the electrode assembly into the battery case, and (b) after injecting the composition for gel polymer electrolyte according to the present invention into the battery case, It may be produced through the steps of polymerizing to form a gel polymer electrolyte.

At this time, the polymerization reaction is possible via an E-BEAM (electron beam), gamma ray, and normal temperature / high temperature aging steps.

On the other hand, the lithium secondary battery according to the present invention may be a lamination-folding type or a lamination-stack type lithium secondary battery. Specifically, in the case of a lamination-stack type lithium secondary battery, a unit including a positive electrode / separation film / negative electrode is subjected to a lamination step of first adhering one or more positive electrodes or negative electrodes and one or more separation films. After forming the cell, a separation film is interposed between the unit cells, the electrode assembly is formed by stacking / welding, the electrode assembly is inserted into the battery case, and then the electrolyte is injected. May be manufactured. On the other hand, in the case of a lamination-folding type lithium secondary battery, the unit cell manufactured through the lamination step is folded using a long separation film sheet to form an electrode assembly, and the electrode assembly is used as a battery case. It may be manufactured by injecting an electrolyte after inserting it into the battery.

At this time, when the separation film for a lithium secondary battery having the first and second coating layers according to the present invention is used, the adhesive force between the gel polymer electrolyte and the separation film is improved by the ethylenically unsaturated group of the first organic binder. Moreover, even in the process of going through the lamination step by the second organic binder contained in the second coating layer, a constant adhesion can be maintained and a unit cell can be stably formed.

Further, as the battery case, various battery cases used in the technical field may be used without limitation, and for example, a cylindrical type, a square type, a pouch type, a coin type battery case and the like may be used. It's okay.

On the other hand, the composition for a gel polymer electrolyte may contain a lithium salt, a non-aqueous organic solvent and a polymerization initiator in addition to the oligomer.

As the lithium salt, those usually used for an electrolyte for a lithium secondary battery may be used without limitation. For example, Li ⁺ is contained as a cation of the lithium salt, and F-, ^{Cl- ,} Br- ^, I- ^, NO _3- ^, N (CN) _2- ^, BF _4- ^, ClO _4- ^, AlO as anions. _4- ^, AlCl _4- ^, PF _6- ^, SbF _6- ^, AsF _6- ^, BF ₂ C ₂ O _4- ^, BC ₄ O _8- ^, (CF ₃ ) ₂ PF _4- ^, (CF ₃ ⁾ ₃ PF _3- , (CF ₃ ) ₄ PF _2- ^, (CF ₃ ) ₅ PF- ^, (CF ₃ ) ₆ P- ^, CF ₃ SO _3- ^, C ₄ F ₉ SO _3- ^, CF ₃ CF ₂ SO _3- ^, (CF 3) ₃ SO ₂ ) ₂ N- ^, (F ₂ SO ₂ ) ₂ N- ^, CF ₃ CF ₂ (CF ₃ ) ₂ CO- ^, (CF ₃ SO ₂ ) ₂ CH- ^, CF ₃ (CF ₂ ⁾ ₇ SO _3- , CF ₃ CO _2- ^, CH ₃ CO _2- ^, SCN- ^, and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- may include at least one selected from the group. The lithium salt may be used alone or in admixture of two or more, if necessary. The lithium salt may be appropriately changed within a range that can be normally used, but in order to obtain an optimum film forming effect for preventing corrosion of the electrode surface, 0.8 M to 2 M in the electrolytic solution, specifically 0. It may be contained at a concentration of 8.8M to 1.5M. However, the concentration range is not always limited, and the gel polymer electrolyte composition may be contained in a high concentration of 2M or more depending on other components.

As the non-aqueous organic solvent, those usually used for an electrolytic solution for a lithium secondary battery may be used without limitation. For example, an ether compound, an ester compound, an amide compound, a linear carbonate compound, a cyclic carbonate compound, or the like may be used alone or in combination of two or more. Typically, a cyclic carbonate compound, a linear carbonate compound, or a mixture thereof may be contained.

Specific examples of the cyclic carbonate compound include ethylene carbonate (ethylene carbonate, EC), propylene carbonate (propylene carbonate, PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene. There is any one selected from the group consisting of carbonate, 2,3-pentylene carbonate, vinylene carbonate and fluoroethylene carbonate (FEC), or a mixture of two or more of these. Specific examples of the linear carbonate compound include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methylpropyl carbonate and ethyl. Any one selected from the group consisting of propyl carbonate, or a mixture of two or more of these may be typically used, but is not limited thereto.

In particular, among the carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate and propylene carbonate, which have a high dielectric constant and are known to dissociate the lithium salt in the electrolyte well, may be used as the highly viscous organic solvent. In addition to such a cyclic carbonate, a low-viscosity, low-dielectric-constant linear carbonate such as dimethyl carbonate and diethyl carbonate can be mixed and used in an appropriate ratio to produce an electrolyte having high electrical conductivity.

Among the non-aqueous organic solvents, the ether compound is any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether, or these. A mixture of two or more of these may be used, but is not limited thereto.

Among the non-aqueous organic solvents, the ester compound includes linear esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate. And any one selected from the group consisting of cyclic esters such as γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, ε-caprolactone, or a mixture of two or more of these. May be used, but is not limited to this.

The polymerization initiator is decomposed in a battery by heat, as a non-limiting example, from 30 ° C. to 100 ° C., specifically from 60 ° C. to 80 ° C., or at room temperature (5 ° C. to 30 ° C.). The oligomer is reacted to form a radical, and the oligomer can be reacted by a free radical polymerization reaction mediated by the radical to form a gel polymer electrolyte.

As the polymerization initiator, ordinary polymerization initiators known in the art may be used, and may be at least one selected from the group consisting of azo compounds, peroxide compounds, or mixtures thereof.

For example, the polymerization initiator is benzoyl peroxide, acetyl peroxide, dialuryl peroxide, di-tert-butyl peroxide, t-butyl. 2 2'-azobis (2-cyanobutane), dimethyl 2,2'-azobis (2-methylpropionate), 2,2'-azobis (methylbutyronitrile), 2,2'-azobis (isobutyronitrile) ) (AIBN; 2,2'-Azobis (iso-butyronityle)) and 2,2'-azobisdimethyl-valeronitrile (AMVN; 2,2'-Azobisdimethyl-Valeronitrol). Azobisisobuty, etc., but is not limited to this.

The polymerization initiator may contain 0.1% by weight to 5% by weight based on the total weight of the oligomer. If the amount of the polymerization initiator exceeds 5% by weight, the unreacted polymerization initiator may remain during the production of the gel polymer electrolyte, which may adversely affect the battery performance. On the contrary, if the polymerization initiator is less than 0.01% by weight, there is a problem that gelation is not performed well even under conditions of a certain temperature or higher.

According to another embodiment of the present invention, a battery module including the lithium secondary battery and a battery pack containing the same are provided. Since the battery module and battery pack include the lithium secondary battery having high capacity, high rate-determining characteristics and cycle characteristics, it is selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems. It may be used as a power source for medium and large-sized devices.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the following examples are merely examples for deepening the understanding of the present invention, and do not limit the scope of the present invention. It is obvious to those skilled in the art that various changes and amendments are possible within the scope of the present description and technical ideas, and it is natural that such modifications and amendments belong to the scope of claims.

[Example]
1. 1. Example 1
(1) Production of First Organic Binder Under a nitrogen atmosphere, vinylidene fluoride (VDF) as a monomer, diisopropylperoxydicarbonate as a free radical initiator, and 1,1,2- as a solvent. Trichlorotrifluoroethane (1,1,2-triculotrifluoroethane) was placed in a reactor cooled to −15 ° C. After that, the reaction product was stirred at 200 rpm while maintaining the temperature at 45 ° C. for the start of polymerization, and the polymerization reaction was carried out so as to polymerize the compound polymerized so that the unit represented by the chemical formula X-1 was repeated. After 10 hours, NaCl was added to replace Cl at the end of the polymerized compound to terminate the polymerization reaction, and the monomer not participating in the polymerization reaction was discharged.

After the polymerized compound was dispersed in an N-methylpyrrole solvent, acrylic acid (acrylic acid) compared with the polymerized compound was added at a molar ratio of 1: 1.1 and maintained at 45 ° C. in the presence of NaOH. While stirring, the mixture was stirred at 200 rpm. After 10 hours, a drying step was carried out at 120 ° C. to obtain a first organic binder in which Cl was substituted with an acrylic oxy group at the terminal.

(2) Preparation of First Coating Layer Composition In 100 mL of N-methylpyrrole solvent, 3 g of the prepared first organic binder and 27 g of aluminum oxide (Al ₂ O ₃ ) as inorganic particles were added to the first coating. A layer composition was produced.

(3) Preparation of Second Coating Layer Composition 3 g of polyvinylidene difluoride (PVdF, weight average molecular weight = 100,000) and 27 g of Al ₂ O ₃ as inorganic particles are added to 72.1 ml of N-methylpyrrole solvent. The second coating layer composition was produced.

(4) Production of Separation Membrane for Lithium Secondary Battery The first coating layer composition is applied onto a polyethylene substrate having a thickness of 10 μm and then dried at a temperature of 100 ° C. to form a first coating layer having a thickness of 4 μm. Formed. After that, the second coating layer composition was applied onto the first coating layer and then dried at a temperature of 120 ° C. to form a second coating layer having a thickness of 6 μm. A separation membrane (20 μm) for a lithium secondary battery was manufactured.

2. 2. Example 2
A mixture of vinylidene fluoride (VDF) and hexafluoropropylene (HFP, hexafluoropolylone) as monomers in a nitrogen atmosphere at a weight ratio of 7: 3, and isopropylperoxydicarbonate as a free radical initiator. Was used as a solvent, and 1,1,2-trichlorotrifluoroethane (1,1,2-trichlorotrifluoroethane) was charged into a reactor cooled to −15 ° C. After that, the reaction product was stirred at 200 rpm while maintaining the temperature at 45 ° C. for the start of polymerization, and the polymerization reaction was carried out so that the unit represented by the chemical formula X-2 was repeated. After 10 hours, NaCl was added to replace Cl at the end of the polymerized compound to terminate the polymerization reaction, and the monomer not participating in the polymerization reaction was discharged.

After the polymerized compound was dispersed in an N-methylpyrrole solvent, acrylic acid (acrylic acid) compared with the polymerized compound was added at a molar ratio of 1: 1.1 and maintained at 45 ° C. in the presence of NaOH. While stirring, the mixture was stirred at 200 rpm. After 10 hours, a drying step was carried out at 120 ° C. to obtain a first organic binder in which Cl was substituted with an acrylic oxy group at the terminal.

Hereinafter, the lithium secondary battery is used in the same manner as in Example 1 except that the first organic binder produced in Example 2 is used instead of the first organic binder produced in Example 1. A separation membrane for use was manufactured.

3. 3. Example 3
The second coating layer composition is applied onto a polyethylene substrate having a thickness of 10 μm and then dried at a temperature of 120 ° C. to form a second coating layer having a thickness of 6 μm. After that, the first coating layer composition was applied onto the second coating layer, and then the first coating layer having a thickness of 4 μm was formed under a temperature condition of 100 ° C. to produce a separation film for a lithium secondary battery. Except for this, a separation membrane for a lithium secondary battery was manufactured by the same method as in Example 1.

4. Example 4
The second coating layer composition is applied onto a polyethylene substrate having a thickness of 10 μm and then dried at a temperature of 120 ° C. to form a second coating layer having a thickness of 6 μm. After that, the first coating layer composition is applied onto the second coating layer, and then the first coating layer having a thickness of 4 μm is formed under a temperature condition of 100 ° C. to manufacture a separation film for a lithium secondary battery. A separation membrane for a lithium secondary battery was manufactured by the same method as in Example 2 except for the above.

[Comparison example]
1. 1. Comparative Example 1
In Example 1, a separation membrane for a lithium secondary battery was produced by the same method except that the second coating layer was not formed.

2. 2. Comparative Example 2
In Example 1, a separation membrane for a lithium secondary battery was produced by the same method except that the first coating layer was not formed.

3. 3. Comparative Example 3
Unlike the above-mentioned example, only the polyethylene base material on which the first and second coating layers were not formed was used as the separation film for the lithium secondary battery.

[Production example] Lithium secondary battery production As a positive electrode active material (LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ; NCM) 94% by weight, as a conductive material carbon black (carbon black) 3% by weight, as a binder 3% by weight of polyvinylidene fluoride (PVDF) was added to the solvent N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode active material slurry. The positive electrode active material slurry was applied to an aluminum (Al) thin film which is a positive electrode current collector having a thickness of about 20 μm and dried to produce a positive electrode, and then a roll press was performed to produce a positive electrode.

Carbon powder as the negative electrode active material, PVDF as the binder, and carbon black as the conductive material were added to the solvent NMP at 96% by weight, 3% by weight, and 1% by weight, respectively, to produce a negative electrode active material slurry. did. The negative electrode active material slurry was applied to a copper (Cu) thin film which is a negative electrode current collector having a thickness of 10 μm and dried to produce a negative electrode, and then a roll press was performed to produce a negative electrode.

An electrode assembly was assembled using the positive electrode, the negative electrode, and the separation membranes produced in Examples 1 to 4 and Comparative Examples 1 to 3, respectively.

Ethylene carbonate (EC): Ethylene methyl carbonate (EMC) = 3: 7 (volume ratio) in 94.99 g of an organic solvent in which 1M LiPF ₆ is dissolved, and 5 g of the compound (n1 = 3) represented by the chemical formula 1-1. , 0.01 g of the polymerization initiator dimethyl 2,2'-azobis (2-methylpropionate) (CAS No. 2589-57-3) was added to prepare a gel polymer electrolyte composition.

After locating the electrode assembly in the battery case, the gel polymer electrolyte composition is injected, stored at room temperature for 2 days, and then heated at 65 ° C. for 5 hours to thermally polymerize the lithium ion containing the gel polymer electrolyte. The next battery was manufactured.

[Experimental example]
1. 1. Experimental Example 1: Initial capacity measurement experiment A lithium secondary battery manufactured using the separation membranes manufactured in Examples 1 to 4 and a lithium secondary battery manufactured using the separation membranes manufactured in Comparative Examples 1 to 3 are used. After forming a formation with 100 mA current (0.1 Crate) for each of the following batteries, 4.2 V, 333 mA (0.3 C, 0.05 C cut-off) CC / CV charge and 3 V, When the 333mA (0.3C) CC discharge was repeated three times, the third discharge capacity was selected as the initial capacity. The results are shown in Table 1.

According to Table 1, in the case of the lithium secondary batteries of Examples 1 to 4, since the adhesive force between the gel polymer electrolyte and the separation membrane is high, a higher initial capacity can be obtained at a high voltage.

On the other hand, in the case of the lithium secondary batteries of Comparative Examples 1 to 3, as shown in Table 1 above, the adhesive strength between the lithium secondary battery contrasting electrolyte of Examples 1 to 4 and the separation film is low, and the interface characteristics are insufficient. Therefore, it can be seen that the initial capacity is relatively low.

2. 2. Experimental Example 2: Cycle (life) measurement Lithium secondary batteries manufactured using the separation membranes manufactured in Examples 1 to 4 and lithium manufactured using the separation membranes manufactured in Comparative Examples 1 to 3. After forming each secondary battery with 100 mA current (0.1 Crate), 4.2 V, 333 mA (0.3 C, 0.05 C cut-off) CC / CV charge and 3 V, 333 mA ( 0.3 C) When the CC discharge was repeated 100 times, the 100th discharge capacity was compared with the initial capacity (the third discharge capacity when the charge / discharge was repeated 3 times), and the capacity retention rate was measured. The results are shown in Table 2.

Examining Table 2 above, in the case of the lithium secondary batteries of Examples 1 to 4, the interfacial adhesion between the gel polymer electrolyte and the separation membrane is excellent, and the distribution of the gel polymer electrolyte is excellent, so that an additional electrolyte is added. It shows the result that the cycle life is improved by suppressing the deterioration reaction.

On the other hand, in the case of the lithium secondary batteries of Comparative Examples 1 to 3, as shown in Table 2 above, the adhesive strength between the lithium secondary battery contrasting electrolyte of Examples 1 to 4 and the separation film is low, and the interface characteristics are insufficient. Therefore, it can be seen that the capacity retention rate after the cycle decreases due to the additional deterioration of the electrolyte.

3. 3. Experimental Example 3: Nail penetration test
Heat generation temperature and ignition when a metal nail with a diameter of 2.5 mm is passed through a fully charged lithium secondary battery manufactured in Examples 1 to 4 and Comparative Examples 1 to 3 at a speed of 600 mm / min. Whether or not it was possible was measured, and a safety evaluation experiment was conducted by mechanical impact and internal short circuit of the lithium secondary battery.

The metal nail caused an internal short circuit of the lithium secondary battery, and the battery generated heat from now on, but the higher the heat generation temperature, the higher the possibility of ignition, so it was evaluated that the safety was vulnerable. In addition, when such heat generation leads to ignition, it was evaluated that the safety of the secondary battery is vulnerable.

As shown in Table 3, the lithium secondary batteries of Examples 1 to 4 of the present invention are excellent in safety because the heat generation temperature is as low as 80 ° C., while the lithium secondary batteries of Comparative Examples 1 to 3 are. It can be seen that the safety is vulnerable because the heat generation temperature of each exceeds 100 ° C. Further, when the safety is evaluated based on the number of ignited cells, it can be seen that the lithium secondary batteries of Examples 1 to 4 are safer.

Claims (13)

With the base material
A first coating layer containing a first organic binder containing an ethylenically unsaturated group,
A separation membrane for a lithium secondary battery, comprising a second organic binder and a second coating layer containing inorganic particles. The separation film for a lithium secondary battery according to claim 1, wherein the first coating layer is formed on the surface of the base material, and the second coating layer is formed on the first coating layer. .. The separation film for a lithium secondary battery according to claim 1, wherein the second coating layer is formed on the surface of the base material, and the first coating layer is formed on the second coating layer. .. The lithium secondary according to any one of claims 1 to 3, wherein the ethylenically unsaturated group contains at least one selected from the group consisting of a vinyl group, an acrylic oxy group and a methacrylic oxy group. Separation film for batteries. The first organic binder and the second organic binder each independently contain a polymer containing at least one unit selected from the group consisting of the chemical formulas X-1 to X-6, according to claims 1 to 4 . Separation film for lithium secondary battery according to any one of the above:

(In the chemical formula X-1, the m1 is an integer from 1 to 100.)

(In the chemical formula X-2, m2 and m3 are independently integers from 1 to 100.)

(In the chemical formula X-3, the m4 is an integer from 1 to 100.)

(In the chemical formula X-4, the m5 is an integer from 1 to 100.)

(In the chemical formula X-5, the m6 is an integer from 1 to 100.)

(In the chemical formula X-6, the m7 is an integer from 1 to 100.) For a lithium secondary battery, which comprises a step of forming a first coating layer containing a first organic binder containing an ethylenically unsaturated group on the surface of a substrate and a second coating layer containing a second organic binder and inorganic particles. Method for manufacturing a separation film. The method for producing a separation film for a lithium secondary battery according to claim 6, wherein the first coating layer is formed on the substrate and then the second coating layer is formed on the first coating layer. The method for producing a separation film for a lithium secondary battery according to claim 6, wherein the second coating layer is formed on the substrate and then the first coating layer is formed on the second coating layer. The temperature condition of the step of forming the first coating layer is 40 ° C. to 110 ° C., and the temperature condition of the step of forming the second coating layer is 120 ° C. to 200 ° C., claims 6 to 8. The method for manufacturing a separation membrane for a lithium secondary battery according to any one of the above. Between at least one unit cell containing at least one positive electrode, at least one negative electrode, and at least one first separation film interposed between the positive electrode and the negative electrode, and the unit cell. It contains an electrode assembly containing a second separation membrane interposed therebetween, and a gel polymer electrolyte formed by polymerizing an oligomer containing a (meth) acrylate group.
The first separation film and the second separation film include a first coating layer containing a first organic binder containing an ethylenically unsaturated group and a second coating layer containing a second organic binder and inorganic particles.
A lithium secondary battery in which the first organic binder containing the ethylenically unsaturated group and the oligomer containing the (meth) acrylate group are polymerized to form a polymer network having a three-dimensional structure. The lithium secondary battery according to claim 10, wherein the oligomer is represented by the following chemical formula 1.

In the chemical formula 1,
The A and A'are units each independently containing a (meth) acrylate group.
The C ₁ is a unit containing an oxyalkylene group. The lithium secondary battery according to claim 10 or 11 , wherein the oligomer contains at least one compound selected from the compounds represented by the following chemical formulas 1-1 to 1-5.

(In the chemical formula 1-1, the n1 is an integer from 1 to 20,000.)

(In the chemical formula 1-2, the n2 is an integer from 1 to 20,000.)

(In the chemical formula 1-3, the n3 is an integer from 1 to 20,000.)

(In the chemical formula 1-4, the n4 is an integer from 1 to 20,000.)

(In the chemical formula 1-5, the n5 is an integer from 1 to 20,000.) The lithium according to any one of claims 10 to 12, wherein the gel polymer electrolyte is formed by injecting a composition for a gel polymer electrolyte containing the oligomer into a battery case and then curing the composition. Secondary battery.